), however, is a radioactive isotope, the other two being stable.
Understanding the ages of related fossil species helps scientists piece together the evolutionary history of a group of organisms.
Pioneers It is often overlooked that throughout the nineteenth century, most of the electrical experimenters, inventors and engineers who made these advances possible had to make their own batteries before they could start their investigations. the World was starting to emerge from the Stone Age. C., Mesopotamians (from modern day Iraq), who had already been active for hundreds of years in primitive metallurgy extracting metals such as copper from their ores, led the way into the Bronze Age when artisans in the cities of Ur and Babylon discovered the properties of bronze and began to use it in place of copper in the production of tools, weapons and armour.
They did not have the benefit of cheap, off the shelf, mass produced batteries. Bronze is a relatively hard alloy of copper and tin, better suited for the purpose than the much softer copper enabling improved durability of the weapons and the ability to hold a cutting edge.
Natural uranium as found in the Earth's crust is a mixture largely of two isotopes: uranium-238 (U-238), accounting for 99.3% and uranium-235 (U-235) about 0.7%.
The isotope U-235 is important because under certain conditions it can readily be split, yielding a lot of energy.